1 2 LDM - Logical Disk Manager (Dynamic Disks)
3 ------------------------------------------
4 5Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>.
6Last Updated by Anton Altaparmakov on 30 March 2007 for Windows Vista.
7 8Overview
9--------
10 11Windows 2000, XP, and Vista use a new partitioning scheme. It is a complete
12replacement for the MSDOS style partitions. It stores its information in a
131MiB journalled database at the end of the physical disk. The size of
14partitions is limited only by disk space. The maximum number of partitions is
15nearly 2000.
16 17Any partitions created under the LDM are called "Dynamic Disks". There are no
18longer any primary or extended partitions. Normal MSDOS style partitions are
19now known as Basic Disks.
20 21If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use
22Dynamic Disks. The journalling allows Windows to make changes to these
23partitions and filesystems without the need to reboot.
24 25Once the LDM driver has divided up the disk, you can use the MD driver to
26assemble any multi-partition volumes, e.g. Stripes, RAID5.
27 28To prevent legacy applications from repartitioning the disk, the LDM creates a
29dummy MSDOS partition containing one disk-sized partition. This is what is
30supported with the Linux LDM driver.
31 32A newer approach that has been implemented with Vista is to put LDM on top of a
33GPT label disk. This is not supported by the Linux LDM driver yet.
34 35 36Example
37-------
38 39Below we have a 50MiB disk, divided into seven partitions.
40N.B. The missing 1MiB at the end of the disk is where the LDM database is
41 stored.
42 43 Device | Offset Bytes Sectors MiB | Size Bytes Sectors MiB
44 -------+----------------------------+---------------------------
45 hda | 0 0 0 | 52428800 102400 50
46 hda1 | 51380224 100352 49 | 1048576 2048 1
47 hda2 | 16384 32 0 | 6979584 13632 6
48 hda3 | 6995968 13664 6 | 10485760 20480 10
49 hda4 | 17481728 34144 16 | 4194304 8192 4
50 hda5 | 21676032 42336 20 | 5242880 10240 5
51 hda6 | 26918912 52576 25 | 10485760 20480 10
52 hda7 | 37404672 73056 35 | 13959168 27264 13
53 54The LDM Database may not store the partitions in the order that they appear on
55disk, but the driver will sort them.
56 57When Linux boots, you will see something like:
58 59 hda: 102400 sectors w/32KiB Cache, CHS=50/64/32
60 hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7
61 62 63Compiling LDM Support
64---------------------
65 66To enable LDM, choose the following two options:
67 68 "Advanced partition selection" CONFIG_PARTITION_ADVANCED
69 "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION
70 71If you believe the driver isn't working as it should, you can enable the extra
72debugging code. This will produce a LOT of output. The option is:
73 74 "Windows LDM extra logging" CONFIG_LDM_DEBUG
75 76N.B. The partition code cannot be compiled as a module.
77 78As with all the partition code, if the driver doesn't see signs of its type of
79partition, it will pass control to another driver, so there is no harm in
80enabling it.
81 82If you have Dynamic Disks but don't enable the driver, then all you will see
83is a dummy MSDOS partition filling the whole disk. You won't be able to mount
84any of the volumes on the disk.
85 86 87Booting
88-------
89 90If you enable LDM support, then lilo is capable of booting from any of the
91discovered partitions. However, grub does not understand the LDM partitioning
92and cannot boot from a Dynamic Disk.
93 94 95More Documentation
96------------------
97 98There is an Overview of the LDM together with complete Technical Documentation.
99It is available for download.
100 101http://www.linux-ntfs.org/ 102 103If you have any LDM questions that aren't answered in the documentation, email
104me.
105 106Cheers,
107 FlatCap - Richard Russon
108 ldm@flatcap.org
109 110